Hydrogen isotopes have extremely important roles in many fields, but they have almost the same chemical and similar physical properties, which makes the separation process very difficult. In this work, ZIF-67 was selected for the separation of hydrogen isotopes. The theoretical calculation results showed that the adsorption selectivity of ZIF-67 for hydrogen isotope mixtures (D 2 /H 2 = 1:1) increased from 1.66 to 2.08 with the temperature decreasing from 77 to 20 K, indicating that ZIF-67 has a chemical affinity quantum sieving (CAQS) effect. Meanwhile, the diffusion coefficients of H 2 and D 2 were also different; the kinetic selectivity of D 2 /H 2 was 4.41 at 70 K, indicating that ZIF-67 has a kinetic quantum sieving (KQS) effect at low temperatures. When the temperature was higher than 72 K, the diffusion coefficient of H 2 was higher than that of D 2 ; ZIF-67 showed a typical kinetic sieving effect and the kinetic selectivity of H 2 /D 2 was 1.29 at 77 K. Based on the fact that due to the CAQS effect, the adsorption capacity of D 2 in ZIF-67 was higher at 77 K and the diffusion coefficient of D 2 was lower at the same time, it is expected that ZIF-67 can effectively realize the separation of hydrogen isotopes. In contrast, ZIF-8, isostructural to ZIF-67, has no difference on H 2 and D 2 in view of adsorption capacity and adsorption heat and, consequently, has no effect on separation, indicating the importance of the incompletely filled d-orbitals (Co 2+ versus Zn 2+ ). To verify the separation performance of ZIF-67, the composites ZIF-67@NH 2 -γ-Al 2 O 3 were synthesized by the layer-by-layer (LBL) method and used as a gas chromatographic stationary phase packed in a 1 m column (1.0 m × 2.0 mm I.D.) for separation of hydrogen isotopes H 2 and D 2 . Under optimal chromatographic separation conditions, the resolution (R) reached 1.79 and the separation time was 5.55 min with the optimal composite ZIF-67@NH 2 -γ-Al 2 O 3 at 77 K.
A series of isostructural compounds Na(HL)(CHCOO)Ln(Al(OH)MoO)(HO)·10HO [L = nicotinate; Ln = Eu (1), Tb (2)] and Na(HL)(CHCOO)EuTbLa(AlMo(OH)O)(HO)·10HO (3-8, L = nicotinate), wherein Anderson-type polyanions AlMo(OH)O as basic inorganic building blocks are connected by Eu(CHCOO)(HL)(HO)] and [Na(HO)] cations, resulting in formation of three-dimensional lanthanide metal-organic open frameworks, were synthesized successfully with AlCl·6HO, NaMoO·2HO, nicotinic acid, and lanthanide nitrates as starting materials. The compounds were characterized by UV-vis, IR, elemental analysis, powder XRD, and TG-DTA measurements. The single-crystal structures of compounds 1 and 2 show that the two compounds display three-dimensional open frameworks with 1D channels along the b and c axes. Investigation of the energy transfer mechanism indicated that the organic nicotinate ligand can transfer energy efficiently to Tb rather than Eu. The influence of the POM moiety on the fluorescence of the compounds is also studied. Compounds 1-8 exhibit tunable luminescence color, and emitting of white light was realized through adjusting the molar ratio of Eu:Tb:La within the compounds.
Composite films with the general formula (POM/CuTAPc) derived from water-soluble Keggin-type polyoxometalates (POMs = HPMoVO, HSiWO, HPMoO and HPWO) and water-insoluble 4,9,16,23-copper tetraaminophthalocyanine (denoted CuTAPc) are successfully fabricated by a layer-by-layer self-assembly technique and systematically characterized. The structure of the polyoxometalate anions in the multilayers is kept intact; the deposition amounts of POM and CuTAPc remain constant in every adsorption cycle of the composite film assembly process. The nonlinear optical properties of the composite films were studied by a Z-scan technique at a wavelength of 532 nm and a pulse width of 7 ns. The results not only show that the composite films exhibit notable optical nonlinear self-defocusing behavior and a saturated absorption effect with the nonlinear optical absorption co-efficient β, refractive index n, and third-order NLO susceptibility χ of the films increasing with the increase in number of layers of the films, but also reveal importantly that the discrepancy of LUMO levels between CuTAPc and POMs is proportional to their third-order NLO response.
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